Something else that just occurred to me: I’d pay to have more sheltered benches at Memphis bus stops, and also hire people to make sure the garbage cans thereabouts are emptied more regularly.
It counts as frivolous because there’s nothing much that can be done to save Memphis from the cesspool its inhabitants seem intent on making it into.
After much thought, I have always wanted to go gambling with my best friend in Vegas. I would pay for our tickets, give him maybe 100k spending money, and we would go during either the NFL or NBA playoffs.
Premium gas for my car.
A Tesla Roadster, with a specially built safety cage surrounding the passenger seat to make it safe for Celtling to ride up front.
A Faberge egg.
This house: Castle in Down - Narrow Water Castle County Down Ireland | Castles In Ireland
A cave house, very high end audio and video, so I could lay around and watch sci-fi, pron, mysteries, drink beer and eat peanuts and get lipo-sucked each year.
A C-130 outfitted with an internal travel trailer, lots of soundproofing and room for my car of the moment and motorcycle of the moment.
Trust funds for my kids, nieces & nephews.
Sorry, I’ll be needing that house to justify my huge garden maze.
First, I would rent a chauffered limousine with a sun roof.
Then, I would pick up several of my old drinking buddies.
We would then proceed to the liquor store. And it will be only the best hootch for us, thanks.
We would then make our way to a novelty shop or some such place where we would purchase a tank of helium.
Afterwards, we would repair to the nearest adult novelty store where we would buy dozens of blow up dolls.
We would then spend the day driving around town, imbibing heroically whilst inflating the blow up dolls with helium and releasing them through the sun roof. With Led Zeppelin and Deep Purple playing loudly on the 8-track, of course.
I’d prefer a Case. That way I could keep it in my grudge to mow my grounds just because my wife could turn out to be a nagger before the dee-vorce.
(And if you actually remember and get that old joke I will have to add extra dino-blood and glitter to my Oakminster shrine on the cave wall) 
A Porsche 935, an aquarium big enough to keep a sperm whale in (plus whale), and one of those giant chessboards they put near hotel swimming pools where the pieces are waist-high.
ETA:
Okay, forget that stuff. THIS is what I’m doing.
My fuck-you-money dream house has a large 2nd floor suite for me with space for a library, walk in closet, a couch, bathroom with a big tub and shower, and two large bedrooms just for me with a king sized bed in each room.
One of the bedrooms will just have closet space, a window and open into the bathroom.; and this bedroom will have a ceiling fan but there will be no tv, no alarmclock, nor computer in this room. Nothing to do in that room but sleep and sex. I’ll leave computer hookup in the library.
I’ve always wanted to own an authentic katana from the Japanese feudal period. That, and I’d use my new-found connections to track down and purchase Alexander the Great’s silver ring.
A submarine - like this, only better
I have read about that and see no way it could possibly be fitted with weapons. What’s the point of a sub without weapons?
You want to deal with teenage angst all over again? 
A whole tank?!?
That’s (part of) what I meant by “better”.
The ability to dive more than 5’ and carry more than one passenger would be the other part.
I shall call mine “Stingray”, of course.
If Athena had not intended for us to massacre one another with more and more elaborate weapons until at last the Earth was reduced to a smoking wasteland inhabited primarily by geese, She would have killed her half-brother with the limp long ago. Who are you to question Athena?
I guess I would try out my idea for a whole-house underfloor vacuum (flip it on and the dust gets sucked through the floor cracks/carpet/rug/whatever).
And a sauna.
That’s all I can come up with.
A 300-seat gaslight-style live theatre. Lots of brass, red velvet curtains, decor is sort of steampunk/candy box. From there I fund my own repertory theater company.
And a helicopter for my husband - mabye an MD-500. I’ve always liked the way those look.
EITHER
An honest-to-god, historically accurate, Vauban-style fortress. The guns need not be real, but they must look and feel real.
OR
A tank collection to rival the Royal Armored Corps Museum in Bovington.